Abstract

We report on the photodissociation dynamics of tert-pentyl bromide near 265 nm investigated by time-sliced velocity map imaging. The speed and angular distributions have been analyzed for both the ground-state Br(2P3/2) atom (denoted Br) and the spin–orbit excited-state Br(2P1/2) atom (denoted Br*). The speed distributions of Br and Br* atoms are all found to consist of three Gaussian components, which correlate to three independent dissociation pathways on the excited potential energy surfaces: (1) the high translational energy (ET) component from the prompt dissociation along the C–Br stretching mode, (2) the middle ET component from the repulsive mode along the C–Br stretching coupled with some bending motions, and (3) the low ET component from the repulsive mode along the C–Br stretching coupled with more bending motions. More interestingly, we have also observed the ions in 263–267 nm. The near-zero kinetic energy distributions extracted from the three images near 265 nm show the typical characteristics that are attributable to multiphotondissociativeionization, suggesting the existence of a neutral superexcited state of the parent tert-pentyl bromide molecule. The contribution of bromine atoms formed in this dissociativeionization channel adds in the total relative distribution of low ET component in the Br*(Br) formation channel, which reasonably explains the abnormal distributions observed in between the middle and low ET components in the Br*(Br) formation channel.

Received 12 August 2011Accepted 01 December 2011Published online 22 December 2011

Acknowledgments:

This work is supported by the National Natural Science Foundation of China (Grant No. 20873133) and the Ministry of Science and Technology of China (Grant Nos. 2007CB815203 and 2010CB923302). The authors would also like to thank the partial support from the Chinese Academy of Sciences (Grant Nos. KJCX2-YW-N24 and KJCX2-EW-W09), the Fundamental Research Funds for the Central Universities of China (Grant No. WK2340000012), and the USTC-NSRL Joint Funds (Grant No. KY2340000021).